1. Field of the Invention
This invention relates to the false twist processing of multi-filament and mono-filament synthetic fibers, particularly polyester and nylon fibers with fiber processing aids applied as spin-finishes subsequent to extrusion of the fibers from the spinneret.
2. Description of the Prior Art
In the production of polyester and polyamide filament, the addition of a chemical coating after extrusion from the spinneret is essential in order to process the emerging filaments into fibers. These coatings are termed in the art "Spin-Finishes" and since the introduction of the first synthetic fiber the provision of such processing aids or lubricants has involved considerable effort on the part of producers of lubricant compositions. It was realized early that the polyoxyethylene glycols obtained either by reaction of ethylene oxide with an aliphatic monocarboxylic acid or a mono- or dihydroxy alcohol would provide a lubricant having a balance of properties besides lubricity that would suit such materials for this application. For instance, water solubility or dispersibility, heat stability and the ability of the lubricant to impart a degree of antistatic properties to the synthetic filament are desirable in addition to the property of lubricity which is the prime consideration in the selection of such fiber lubricants.
Over the years, fiber lubricants for synthetic filaments and yarn have utilized, either alone or in mixtures, such alkylene glycol derivatives as the alkoxylated stearic acid esters disclosed in U.S. Pat. No. 2,910,490 and U.S. Pat. No. 1,970,578 or a polyoxypropylene compound having 10 to 20 recurring units and capped by a lower alkyl or lower acyl group as disclosed in U.S. Pat. No. 3,446,734. Recently, esters of an ethoxylated alcohol have been disclosed for use in admixture with other lubricant components as fiber treating compositions as disclosed in U.S. Pat. No. 3,578,594.
There is a current tendency toward the use of heteric polyoxyalkylenes as components of fiber lubricants. These have low viscosity at room temperature and their viscosity does not change appreciably upon heating to elevated temperatures during processing of the synthetic fiber. Such compositions are disclosed in U.S. Pat. No. 2,425,755 as mixtures of polyoxyalkylene compounds which are aliphatic monoethers of polyoxyalkylene glycols. These compositions are composed of mixtures of oxyethylene and oxypropylene groups in the chain and contain at least one-third part of propylene oxide for each part of ethylene oxide. Similar compositions based upon aliphatic diols are disclosed in U.S. Pat. No. 2,425,845. Heteric polyoxyalkylene monoethers having polyoxyalkylene hydroxyl groups blocked with the residue of a lower alkyl or an acyl group are disclosed in U.S. Pat. No. 3,756,972 and U.S. Pat. No. 3,338,830.
It was not until the disclosure of U.S. Pat. No. 2,457,139 that further reduction in viscosity at ambient temperatures was obtained by reacting the oxyalkylene diols of U.S. Pat. No. 2,425,755 with C.sub.4 to C.sub.18 fatty acids. It was then realized that the advantageous lubricating effects of a higher fatty acid such as stearic acid could be obtained in combination with the lubricating effect of the oxyalkylene moiety by reacting an oxyalkylene glycol with a fatty acid to produce a heteric polyoxyalkylene glycol lubricant for polyester yarn as disclosed in U.S. Pat. No. 3,925,588 and German Offen. No. 2,516,736. Such products were substantially improved with respect to reduced viscosity as compared to the ethoxylated fatty acid esters long known to the art as illustrated by the compositions disclosed in U.S. Pat. No. 2,910,490, cited above. Such lubricant compositions while representing substantial advances over early prior art compositions would be of greater utility if further reduction in viscosity could be achieved so that such compositions could be applied without water dilution, if desired. Other prior art references of interest are: U.S. Pat. No. 3,539,518; U.S. Pat. No. 3,146,272 and U.S. Pat. No. 3,578,594.